Patent US3855618A successfully refreshed from Google Patents.
US3855618A
Expired / Lapsed
US
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Magnetic head having variable gap length
Assignee: US Philips Corp
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Filing: 1973-10-09
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Granted: 1974-12-17
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Expires: 1993-10-09
Abstract
Abstract A magnetic head being provided with at least one electromechanical transducer, in which the distance between the gap bounding faces can be varied so as to be relatively long during recording and relatively short during playback. Electrostrictive transducers are preferably used which are energized by means of a control voltage controlled by a recording signal and a playback signal.
Inventors
- 👤 J Koorneef
- 👤 J Potgiesser
- 👤 A Walraven
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-10-26 15:04
CPC Classifications
G; G11; G11B; G11B5/00; G11B5/127; G11B5/187; G11B5/245; G11B5/2452
Claims Analysis
Total Claims: 9
Claim 1
Independent Claim
115 words
A magnetic head for recording and playing back which comprises: a core including first and second magnetizable pole pieces, each magnetizable pole piece having a gap bounding face, said gap bounding faces being disposed in generally opposed relation forming a transducing gap, at least one of said magnetizable pole pieces having secured thereto means for displacing said magnetizable pole piece between a recording position and a playback position thereby changing the gap length between said gap bounding faces, said means comprising an electrostrictive transducer responsive to a control voltage applied thereto, said control voltage being varied responsive to the recording mode of operation of the head and the playback mode of operation of the head.
Claim 2
Dependent Claim
115 words
A magnetic head for recording and playing back which comprises: a core including first and second magnetizable pole pieces, each magnetizable pole piece having a gap bounding face, said gap bounding faces being disposed in generally opposed relation forming a transducing gap, at least one of said magnetizable pole pieces having secured thereto means for displacing said magnetizable pole piece between a recording position and a playback position thereby changing the gap length between said gap bounding faces, said means comprising an electrostrictive transducer responsive to a control voltage applied thereto, said control voltage being varied responsive to the recording mode of operation of the head and the playback mode of operation of the head.
Claim 3
Dependent Claim
32 words
The apparatus as described in claim 1 wherein each of said magnetizable pole pieces carries means for displacing said magnetizable pole piece to vary the gap length between said gap bounding faces.
Claim 4
Dependent Claim
77 words
The apparatus as claimed in claim 2 wherein each of said electrostrictive transducers has a generally planar face and each of said magnetizable pole pieces has a generally planar face, each Of said electrostrictive transducers secured on said magnetizable pole pieces being disposed with the generally planar faces thereof being disposed in co-planar relationship, each of said electrostrictive transducers upon application of at least one control voltage bending the arm on which the particular transducer is carried.
Claim 5
Dependent Claim
45 words
The apparatus as claimed in claim 1 wherein said first and second magnetizable pole pieces comprise portions of discrete core halves which enclose a winding aperture, said halves being rigidly secured together in a first place and enclosing the recording gap in a second place.
Claim 6
Dependent Claim
32 words
The apparatus as described in claim 4 wherein said electrostrictive transducers are secured throughout their length to oppositely disposed planar surfaces and the control voltages supplied to said transducers have opposite signs.
Claim 7
Dependent Claim
32 words
The apparatus as described in claim 4 wherein said electrostrictive transducers are secured throughout their length to oppositely disposed planar surfaces and the control voltages supplied to said transducers have same signs.
Claim 8
Dependent Claim
40 words
The apparatus as described in claim 1 wherein two electrostrictive transducers are carried by said first and second magnetizable pole pieces and are disposed generally at right angles thereto and the control voltages supplied to said transducers have opposite signs.
Claim 9
Dependent Claim
48 words
The apparatus as described in claim 1 wherein plates of non-magnetizable material are carried on said magnetizable pole pieces, said plates having planar surfaces which are parallel to said gap bounding faces, said plates projecting beyond said magnetizable pole pieces and being mechanically coupled together by electrostrictive transducers.
References Cited (Backward Citations)
USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
|---|---|---|---|---|---|
| 3.5 Years (Year 4) | 1977-12-16 | 1978-06-17 | 1978-12-17 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1981-12-16 | 1982-06-17 | 1982-12-17 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1985-12-16 | 1986-06-17 | 1986-12-17 | $7700.00 | Window Closed / Lapsed |